From: Andrew Morton <akpm@linux-foundation.org>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: rpjday@crashcourse.ca, linux-mm@kvack.org
Subject: Re: [PATCH] MM: Rewrite some tests with is_power_of_2() for clarity.
Date: Mon, 27 Apr 2009 12:58:39 -0700 [thread overview]
Message-ID: <20090427125839.19d23850.akpm@linux-foundation.org> (raw)
In-Reply-To: <20090427170428.GA1890@cmpxchg.org>
On Mon, 27 Apr 2009 19:04:28 +0200
Johannes Weiner <hannes@cmpxchg.org> wrote:
> > @@ -438,7 +439,7 @@ static void * __init alloc_bootmem_core(struct bootmem_data *bdata,
> > align, goal, limit);
> >
> > BUG_ON(!size);
> > - BUG_ON(align & (align - 1));
> > + BUG_ON(!is_power_of_2(align));
>
> Note that this is no 1:1 translation. align could be zero before but
> not anymore. Have you checked whether all callsites are ready for
> this? The common bootmem macros use alignment to cacheline or page
> boundary. I haven't checked all callsites that might use __api,
> though.
>
> OTOH, it's doubtful that 'no alignment' should be expressed as 0
> instead of 1.
>
> Still, it probably makes sense to express this change in semantics in
> the changelog.
ooh, yeah, well spotted. There may well be code out there which sets
align=0.
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prev parent reply other threads:[~2009-04-27 20:00 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-04-24 12:46 [PATCH] MM: Rewrite some tests with is_power_of_2() for clarity Robert P. J. Day
2009-04-27 15:59 ` Christoph Lameter
2009-04-27 17:04 ` Johannes Weiner
2009-04-27 19:58 ` Andrew Morton [this message]
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